This looks really clean, thanks for sharing! Does it work with custom domains too, or is it localhost only? I've got a project that needs to test against a specific domain locally.
localhost only for now — portname works with *.localhost subdomains
which browsers resolve automatically so no config needed.
for custom domains like myapp.company.com you'd need to manually add
it to your hosts file (/etc/hosts on Mac/Linux,
C:\Windows\System32\drivers\etc\hosts on Windows) pointing to 127.0.0.1.
custom domain support is something i'd like to add in future